FR3024053A1 - GAS INJECTION ELEMENT IN A REGENERATOR OF A FLUID CATALYTIC CRACKING UNIT - Google Patents

Abstract

An injection element (10) for a gas injection system (1) inside a regenerator of a fluid catalytic cracking unit, said injection element defining a passage (12) and being arranged so as to be fixed on a support (11) so that said passage opens on the one hand to a cavity and on the other hand to a fluidized catalytic bed, characterized in that said injection element is made of ceramic material .

Description

FIELD OF THE INVENTION The invention relates to the injection of gas, for example air, into a regenerator of a fluid catalytic cracking unit or FCC. English "Fluid Catalytic Craking"). Fluid catalytic cracking is a petroleum refining process which consists in reducing the size of hydrocarbon molecules by the action of the temperature in the presence of a solid catalyst, for example alumina. This catalyst is maintained in a fluidized state and circulates continuously inside the cracking unit by passing from a reaction zone to a regeneration zone.

At the reaction zone, the charge to be treated and the catalyst are introduced together in a substantially vertical tubular reactor, which may be upflow, usually referred to as "riser", or downflow usually referred to as "downer". The temperature of the reactor can reach several hundred degrees Centigrade, for example from 520 to 550 ° C. At the level of the regeneration zone, a regenerator comprises an enclosure in which the coke deposited on the catalyst by the cracking of the charge is burned. This combustion of the coke makes it possible to restore its activity to the catalyst and supplies it with the energy necessary for heating, vaporizing and cracking the feedstock fed into the tubular reactor. The combustion reaction of the coke requires an oxygen supply. This is mainly provided by air. The combustion carried out inside the regenerator can be total or partial depending on whether or not the entire coke is burned. This reaction produces carbon dioxide. The catalyst thus regenerated is fed to the inlet of the tubular reactor. The temperature in the regenerator is of the order of 600 ° C to 700 ° C.

There are air injection systems, to provide the air necessary for the combustion of coke, designed to provide a relatively uniform and stable fluidization of a catalyst bed. For example, there is known a perforated tray system supporting the entire pass section of the catalytic bed. Pressurized air passes through the perforated tray from bottom to top, passing through injection nozzles of the perforated tray. These nozzles, made of special steels, having increased abrasion resistance, nevertheless have to be replaced regularly because of relatively high abrasion. The erosion of the steel by the catalyst is indeed likely to cause a rupture of the injection nozzles and / or, in particular when the catalyst enters the interior of the nozzles, an abrasion of the inner walls of the nozzles or an air injection cavity upstream of the plate, which may adversely affect the performance of the regenerator. These special steel nozzles are sometimes subjected to a surface treatment to enhance their resistance to erosion, for example by a titanium nitride deposition. This deposit is generally of the order of a few tens to a few hundred gm. However, if the erosion of such a coating is slow, given its hardness, it is found that when the coating is completely eroded, the erosion of the support metal is then very fast and leads to the destruction of the coating. nozzle. Another method, allowing deposition of erosion resistant materials to greater thicknesses than previously, is detailed in published patent application CN101104814, which discloses a composite nozzle in the form of a cylindrical tube section, comprising a ceramic part, a transition layer and a part of austenitic steel. The ceramic described is an alpha alumina. The method of manufacturing the nozzle comprises (1) a first deposition of a mixture of alumina and iron to form a transition layer on the inner surface of the cylindrical tube section, and (2) a deposit of a ceramic such as alumina to a thickness of about 3 to 10 mm by centrifugation on the transition layer. The inventors claim a doubling of the service life in an FCC at a temperature of 800 ° C. Despite the improvements reported in the literature, there is therefore a need for a system for which maintenance could be less restrictive.

There is provided an injection element for a gas injection system inside a regenerator of a fluid catalytic cracking unit. This injection system comprises a support 3024053 3 defining at least one orifice, this support comprising a wall defining at least a portion of a cavity and having a first face intended to be in contact with the gas contained in this cavity, and the support comprising a second face, opposite to the first face, intended to be in contact with a fluidized catalytic bed. This injection element defines a passage and is arranged to be secured to the support, at the orifice, so that gas from the cavity can flow via the passage to the fluidized catalytic bed. According to the invention, this injection element is made of ceramic material. Such an injection element, for example an injection nozzle, may have an abrasion resistance caused by the flow of catalyst passing in contact with the injection element by a relatively high vortex effect, so that this injection element can be replaced less often than in the prior art. In addition, the design constraints, in particular the constraints related to the erosion induced by the catalyst particles, may be less important than in the prior art. It is thus possible to design gas injection elements with an optimized shape in order to allow a better distribution of the gas within the regenerator, which can thus make it possible to better preserve the quality of the catalyst. In particular, the number and the intensity of the hot spots within the regenerator can be reduced compared with the prior art.

In addition, the weight of this injection element may be less than the weight of a steel injection element of the type known from the prior art. In addition, the injection element may be designed with a passage having a larger cross-section than in the prior art, such that the number of injection elements and / or the pressurization of the gas in the cavity may be reduced (s). Thus, a characteristic of the invention lies in the fact that the injection element is made entirely from a ceramic material. The injection element is thus made of ceramic at least for its main elements, which includes a hollow cylindrical body defining the passage for the gas.

The ceramic materials have a relatively high hardness, namely a hardness of at least 1400N / mm2 in Wickers hardness. Preferably, the ceramic material has a hardness greater than 2100 N / mm 2 or greater than 2500 N / mm 2.

The ceramic materials have been found to be suitable for the conditions of use of an FCC unit. In particular, these materials may have good resistance to corrosion and temperature. Preferably, the ceramic material may be selected from silicon carbide SiC, boron carbide B4C, silicon nitride Si3N4, aluminum nitride A1N, boron nitride BN, alumina A1203, or mixtures thereof. of these. Preferably, the ceramic material is SiC silicon carbide. Preferably, the ceramic material is silicon carbide SiC or comprises silicon carbide SiC, preferably in a major amount, for example in a content of 60% to 99.9% by weight. Silicon carbide has the advantage of having good mechanical and physical properties for a reasonable manufacturing cost.

Alternatively or optionally in combination, the ceramic material may comprise a ceramic matrix, for example selected from silicon carbide SiC, boron carbide B4C, silicon nitride Si3N4, aluminum nitride A1N, boron nitride BN, alumina A1203, or mixtures thereof. In this ceramic matrix are incorporated fibers, for example carbon fibers, ceramic fibers, a mixture of these fibers, or the like. The ceramic material is then a composite material. Such a composite material may be advantageous for the injection elements subjected to stretching and shear stresses. In particular, the fibers may be randomly (pseudo-isotropic) or anisotropic. When present, these fibers may represent from 0.1 to 10% by weight of the composite material. The carbon fibers may be carbon fibers with the graphitic planes oriented along the fiber.

The ceramic fibers may be selected from crystalline alumina fibers, mullite fibers (3A1203, 2SiO2), crystalline or amorphous silicon carbide fibers, zirconia fibers, silica-alumina fibers, or mixtures thereof. For example, the composite ceramic material comprises an SiC silicon carbide matrix comprising fibers of the aforementioned type. The fibers may for example be silicon carbide fibers. Advantageously and without limitation, the ceramic material may be a sintered ceramic material. This can in particular facilitate the realization of the injection element, whether it is a single piece or several pieces. With regard to the size of the injection elements, it is possible to produce the solid ceramic injection element in one piece without assembly or welding. In this case, the injection element may be formed, for example, by molding or by extrusion, followed by firing of the green injection element, under conventional operating conditions adapted to the type of ceramic produced. The cooking step is optionally preceded by a drying step. In a particular embodiment, the injection element may be made in one piece of ceramic material, obtained by sintering. The sintering step may be preceded by a conventional shaping step, for example by compression, extrusion, injection. Sintering is a part manufacturing process consisting of heating a powder without leading it to fusion. Under the effect of heat, the grains are welded together, which forms the cohesion of the part. Sintering is used in particular to obtain the densification of ceramic materials and has the following advantages: it makes it possible to control the density of the material; since one starts from a powder and that it does not melt, one can control the size of the grains of powder (granulometry) and the density of the material, according to the degree of initial compacting of the powders; it allows to obtain controlled porosity materials, chemically inert (low chemical reactivity and good resistance to corrosions) and thermally; It makes it possible to control the dimensions of the parts produced: since there is no change of state, the variations in volume and dimensions are small relative to the melting (no shrinkage phenomenon). In another particular embodiment, the injection element may comprise several pieces of ceramic material 5 assembled together. Advantageously and without limitation, the inner and / or outer walls of the injection element may be smooth, that is, they may have a low surface roughness. Such smooth walls make it possible to improve the flexural strength of the injection element. As a result, it is possible not only to design injection elements with relatively small dimensions, but also to provide for increased gas flow rates. This may make it possible to increase the number of injection elements, and generally, to homogenize the injection of gas into the fluidized bed.

Such a smooth wall can be obtained when the ceramic material is a sintered ceramic material. Advantageously and in a nonlimiting manner, the injection element can be obtained from a relatively fine sintering powder, for example with an average grain diameter of less than or equal to 500 nm, which can lead to surfaces relatively smooth. Alternatively or in addition, the injection element can be obtained by adding to the main material, for example SiC, an additive selected from boron B, silicon Si and carbon C, or mixtures thereof, for example in a proportion ranging from 0.3% to 2% by weight. In the case of a SiC material obtained by sintering of powder, such an addition of additive can make it possible to reduce the porosity and consequently the roughness. Advantageously and in a nonlimiting manner, the additive may comprise a mixture of boron B, silicon Si and carbon C. It is thus possible to form additional SiC, which clogs the pores and thus reduces the roughness. Alternatively or in addition, it may for example provide an additional deposition step of SiC by chemical vapor deposition or CVD (the "Chemical Vapor Deposition").

In general, the invention is not limited by manufacturing the injection element so as to obtain a relatively low porosity. For example, SiC injection nozzles with a relatively high porosity can be made by providing that the pores will be filled as a result of carbon deposits in the regenerator. The injection element may have dimensions of the order of ten centimeters, or other. For example, an injection element may have a height of nearly 15 centimeters, and a ratio between the height and the width varying between 2 and 6. Thus, for an injection element with a nozzle of generally cylindrical shape with a support flange on the support, the outer diameter of the flange 10 may be 5 or 6 centimeters, while the inner diameter of the passage may be 1 or 2 centimeters. The invention is not limited to a particular passage form. It may for example provide a cylindrical passage, but also a passage with a portion of lesser section. In the latter case, this nozzle shape, with a Venturi effect, may tend to limit catalyst entry into the passage. It is furthermore proposed a gas injection system for injecting gas into a regenerator of a fluid catalytic cracking unit, this system comprising at least one injection element as described above and the support . The catalyst may be alumina, or the like. The gas can be air, or whatever. The invention is not limited to a particular form of the support. The support may comprise a single wall separating the air cavity from the catalytic bed, or several walls, for example two superimposed walls. In the latter case, the first surface of the support, in contact with the air cavity, may be a lower surface of the lower wall, and the second surface, in contact with the fluidized bed, may be an upper surface of the wall. higher.

The support may comprise a wall of the regenerator enclosure itself, in which case the injection element may be mounted on the regenerator, but advantageously, the support is designed to be introduced inside the regenerator. For example, it is possible to provide a plate supporting the fluidized bed and covering the whole of a section of the regenerator chamber, so as to form a cavity at the bottom of the regenerator, this plate being able to be flat, concave, convex, or other. The plate 3024053 is advantageously made of a material having a thermal expansion coefficient close to that of the walls of the regenerator enclosure, for example steel, to ensure a relatively good seal between the periphery of the tray and the enclosure .

Alternatively, a conduit may be provided to be immersed in the fluidized bed and defining a cavity within the conduit for supplying gas. The outer surfaces of this duct are thus intended to be in contact with the fluidized bed. For example, the invention may be implemented on a pipe network 10 ("pipe grid" in English). The invention is also not limited to a particular form of the injection element. It is possible, for example, to provide injection elements defining a rectilinear gas flow path, for example with a cylindrical passageway open over a whole section of this passage towards the fluidized bed and / or towards the cavity, or even injection elements defining a more complex gas flow path, with bends for example. These latter injection elements may be advantageous in that with such a complex path the catalyst flowing in the opposite direction to that of the air is less likely to reach the cavity, even if the pressure drop on one side and the other of the support remains relatively limited. In particular, the injection element may be of the cap dispenser type, that is to say that this injection element may comprise a cap portion forming an obstacle to a rectilinear flow path of the air, and defining (one or) transverse gas outlet ports so that the air flow path forms a bend. The cap portion serves to protect the passage in the sense that this cap portion may form a barrier for catalyst particles capable of entering the injection member. The injection element may define (one or) transverse gas inlet orifices, for example oblique orifices with respect to a longitudinal direction of the passage. The injection member may comprise a solid bottom, closing the passage at its upstream end, so that the air entering the passage must flow through the oblique orifices. Thus, the catalyst particles entering the passage 3024053 9 will tend to remain at the bottom of the injection member, rather than back up and flow (countercurrently) through the oblique orifices. It is thus possible to limit the intrusion of catalyst into the air cavity. In one embodiment, the injection element is shaped so that the gas flowing through the passageway is injected via a plurality of orifices of smaller dimensions than those of the passageway. The injection element may for example have a shower head shape. In one embodiment, the support, particularly when it is a conduit, may be made of ceramic material, especially of the aforementioned type, for example SiC obtained by sintering. In one embodiment, at least one, and preferably each injection element is made in one piece with the support. Alternatively, it will be possible to provide an assembly of the injection element or elements to the support.

The invention is in no way limited to the supports of ceramic material. For example, it is possible to provide a metal support, advantageously provided with an anti-erosion coating on its side in contact with the catalytic bed, for example made of concrete, in order to resist the abrasion caused by the catalyst. In this case, the injection elements 20 are advantageously shaped so that their end opens above the anti-erosion coating on the side of the plate in contact with the catalytic bed. Advantageously and in a nonlimiting manner, for at least one and preferably each injection element, the injection system comprises a device for fixing this injection element on the support, said device being able to absorb a difference of dilation between the support material, for example metal, and the ceramic material of this injection element. For example, the fixing device may consist of a layer of materials essentially comprising assembled ceramic fibers having a non-zero elastic modulus, this layer being disposed between a portion of ceramic material and a metal part and ensuring the cohesion of these parts. . Alternatively, the geometry and dimensions of the fastener may be adapted to compensate for the difference in thermal expansion between the metal and the ceramic material.

Advantageously and in a limiting manner, for at least one and preferably each injection element, the fixing device associated with this injection element comprises one (or more) plating element able to exert a force on this element of injection. injection to press this injection element against the support, especially when it is a tray. Thus, the fastener supports the differential expansion between the material of the support, for example a steel, and the material of the injection device. Indeed, the ceramic may have a coefficient of thermal expansion much less than that of steel. The plating element may for example comprise spring means, or the like. For example, one or more tabs secured to (or in one piece with) the support, for example welded to the support, may be provided. These tabs, on the one hand welded at one end to the support, while the other end rests on a surface of the injection element, make it possible to exert an elastic bearing force on the injection element , when it is installed on the support, so as to keep this injection element pressed against the support. This other end may have a relatively flat surface to limit areas of high mechanical stress. Advantageously and in a nonlimiting manner, the injection element may define a bearing portion, shaped to rest on at least a portion of the periphery of an orifice of the support and advantageously all around this orifice when the plating member (s) exerting a force on that bearing portion. The support portion may for example have a general flange shape. The bearing portion may define a bearing surface against which the plating means exerts a force, and, on the opposite side to the bearing surface, a contact surface for contacting around the bearing surface. port of the support. In one embodiment, it will be possible to provide a fixing spring of the type of those used to fix halogen lamps in a false ceiling, surrounding the injection element and maintaining this injection element on the support.

Advantageously and in a nonlimiting manner, the gas injection element can be arranged to prevent lateral displacements beyond a certain range of displacements, in particular the displacements that can break the fluid communication between the cavity and the passage of this gas injection element. In particular, the injection element may define an abutment surface intended to abut against the edge of the orifice in the event of lateral displacement. The passage can thus extend beyond the collar. The injection element may thus have an air inlet portion, through which a portion of the passage passes, and intended to extend in the thickness of the support when the plating means exert a force against the part of the 'support. This air inlet portion may have a smaller diameter than the diameter of the orifice so as to fill the orifice size variations related to the expansion of the steel support. The invention is in no way limited by the shape of this air inlet part, provided that it is suitable for being placed in the orifice of the support. This air inlet portion can thus have a cylindrical shape or the like. In particular, a conical shape may be provided in order to facilitate the positioning of the injection element before the installation of the plating elements.

The invention is also not limited by the shape of the plating element (s). Advantageously, legs may be provided, for example made of steel, advantageously made of abrasion-resistant steel. These tabs extend between two ends, one of the ends being fixed to the support, and the other of the ends being intended to rest on a bearing surface of the injection element. There is also provided a method for installing a gas injection element for a regenerator of a catalytic cracking unit, this injection element being made of ceramic material and defining a passage, the method comprising a step of Positioning the injection element at an orifice of a support, so that the passage of the injection element opens on either side of the support. The method may advantageously also comprise a step of installing one or more plating elements arranged to exert a force on a bearing surface of the injection element, so that injection element is kept pressed against the support.

Furthermore, there is provided a method of manufacturing a gas injection element for a regenerator of a catalytic cracking unit, so that this element defines a passage for the gas, intended to emerge on the one hand. to a cavity, and secondly to a fluidized bed, the method being characterized in that the injection element is made of ceramic material. The method may advantageously comprise a sintering step. The invention will be better understood with reference to the figures, which show embodiments of the invention. FIG. 1 shows an example of a part of a regenerator with an example of an air injection system according to a first embodiment of the invention. FIGS. 2A and 2B are views, respectively in perspective and in section, of an exemplary air injection element according to the first embodiment of the invention, when installed on a tray-type support . Figure 3 is a sectional view of an exemplary air injection element, according to a second embodiment of the invention.

Identical references may be used from one figure to another to designate identical or similar elements in their form or function. With reference to FIG. 1, a regenerator 100 is part of an FCC fluid catalytic cracking unit not shown in its entirety. In this regenerator is carried out the combustion of coke deposited on catalyst from a reactor of the FCC unit. The catalyst in the enclosure 101 of the regenerator 100 forms a fluidized bed 102. An injection system 1 makes it possible to inject air into this fluidized catalytic bed 102, and therefore the oxygen necessary for the combustion of the coke. . This injection system 1 comprises a support, here a perforated plate 11, occupying the whole of a section of the chamber 101, and supporting the fluidized bed 102. This plate defines with the bottom walls 35 of the enclosure a air cavity 103. A conduit 104 opening on this cavity 103 provides air under pressure.

The plate thus comprises a first face 105 in contact with the air of the cavity 103 and a second face 106 in contact with the fluidized bed 102. The perforated plate 11 is made of steel. An anti-erosion coating made of concrete, not shown, also makes it possible to protect the plate from the abrasion associated with the catalyst present in the regenerator. For example, concrete is poured on a not shown steel mesh, for example honeycomb-shaped having a plurality of hexagonal cells secured to each other by their sides ("hex mesh" in English), or other. On each orifice (referenced 19 in FIG. 2B) of the plate 11 is mounted a gas injection element, here an air injection nozzle 10, using lugs 14, or flanges, welded to the plate 11. The injection nozzle 10 is made of ceramic, for example silicon carbide SiC. It is for example formed by injection molding or extrusion. Injection molding or extrusion is traditionally done using ceramic powders or ceramic precursors with a binder. According to another method of manufacture, the ceramic nozzle 10 is formed by compression and heating of a ceramic powder, the compression being able to be maintained during the heating step, the heating step being a sintering step of the ceramic powder. This technique is particularly well suited to the manufacture of solid silicon carbide elements according to the invention. The ceramic powder used optionally comprises ceramic fibers in order to increase the mechanical strength of the parts produced. Ceramic fibers, when present, generally represent from 0.1 to 10% by weight of the part produced. Such a nozzle, made of solid ceramic, has a relatively low manufacturing cost and does not induce significant additional cost compared to a steel having a surface treatment, or a special steel having improved abrasion resistance. With reference to FIGS. 2A and 2B, the injection nozzle 10 defines a passageway 12 in which air is intended to flow from the air cavity towards the catalytic bed, according to the arrows 13.

Plating elements 14, here steel tabs welded to the plate 11, make it possible to exert a pressing force on a bearing surface 15 of a flange 16 of the injection nozzle 10.

Thus, the other side of the flange 16 is pressed on the periphery of the edge of the orifice 19 corresponding to this nozzle 10. If variations in temperature cause a variation in the dimensions of this orifice, the attachment of the nozzle injection 10 thus remains stable despite the possible expansion of the support 11 when the temperature varies. When present, the anti-erosion coating may cover the plating elements 14, it is then preferable to raise the walls defining the passage 12 so that the concrete does not cover it. However, it may be advantageous if the anti-erosion coating does not cover the plating elements 14 to allow free expansion of the different materials. In this case, it is not necessarily useful to raise the walls of the injection nozzles 10. The nozzle 10 further comprises an air inlet portion 17 15 intended to be received inside the orifice 19. This air inlet portion 17 has a generally cylindrical shape in this embodiment. The diameter of this portion 17 is smaller than the diameter of the orifice 19, so that the expansion of the plate 11 does not lead to a rupture of the injection nozzle 10.

The tabs 14 are welded to the plate 11, each tab 14 comprising an end 21 intended to exert a resilient resting force on the flange 16. Each end 21 comprises a plate 22 to avoid the zones of stress too high on the flange 16 of the nozzle 10.

The tabs 16 act as a spring to press the nozzle 10 against the walls of the tray 11. In an embodiment not shown, the air inlet portion could be conically shaped to facilitate the mating. -positioning of the nozzle during the installation of this nozzle.

In the first embodiment, illustrated in FIGS. 1 to 2B, the air inlet portion 17 of the nozzle 10 defines oblique orifices 18. The air flow path thus forms elbows. which is not really troublesome in terms of pressure drop. On the other hand, the catalyst particles falling into the passage 12 from the fluidized bed will tend to remain in the bottom 107 of the nozzle 10, this bottom being full, rather than reaching the air cavity via these oblique orifices 18 This type of air inlet portion may be of interest inasmuch as the walls of the air cavity may be free of abrasion resistant concrete lining. The oblique orifices are arranged slightly offset from each other, so that the pressurized air entering the nozzle 10 has a tendency to form a vortex, in order to evacuate to the fluidized bed any catalyst particles present in the bottom 107 of the nozzle 10. Referring to Figure 3, the injection nozzle 10 ', here shown maintained on a plate 11' with tabs 14 'exerting a support 10 on a flange 16' of the nozzle , comprises a cap portion 201 covering a passage 12 ', so that the air flowing via this passage 12' is injected towards the catalytic bed via oblique outlet orifices 203, according to the arrows 203. This type of nozzle can make it possible to to limit the entry of catalyst particles into the interior of the nozzle. The passage 12 'may thus have a section of relatively large dimensions, which may be advantageous in that the needs for air pressurization terms may then be less than when the nozzles have sections of smaller dimensions, and / or 20 in that less injection nozzles can be provided than in the prior art. In a variant not shown, it would of course be possible to combine the air outlet portion of the second embodiment with a hat portion with the air inlet portion of the first embodiment. The invention can make it possible to design nozzles 10 with a greater freedom of design as to the form insofar as it is less necessary than in the prior art to take into account the problem of erosion by the catalyst.

In particular, it will be possible to provide a shape that makes it possible to optimize the injection of air, which can make it possible to improve the quality of combustion, and thus to further preserve the catalyst, which can be beneficial for the environment. In addition, the maintenance operations, likely to impose stops and / or limit catalytic cracking, can be performed with a lower frequency than in the prior art.

Finally, this type of injection system can be more reliable than in the prior art and thus allow to limit the risk of stopping unscheduled catalytic cracking.

Claims (10)

REVENDICATIONS1. Injection element (10, 10 ') for a gas injection system (1) inside a regenerator (100) of a fluid catalytic cracking unit, said injection system comprising a support ( 11, 11 ') defining at least one orifice (19), this support comprising a wall defining at least a portion of a cavity (103) and having a first face (105) intended to be in contact with the gas contained in this cavity, and the support comprising a second face (106), opposite to the first face, intended to be in contact with a fluidized catalytic bed (102), wherein said injection element defines a passage (12, 12 ') and is arranged so as to be secured to the support, at the orifice, so that gas from the cavity can flow via the passage to the fluidized catalytic bed, characterized in that said injection element is made of material ceramic. 2. Injection element (10; 10 ') according to claim 1, wherein the ceramic material is silicon carbide SiC or comprises SiC silicon carbide, preferably in a majority amount. 3. Injection element (10; 10 ') according to any one of claims 1 or 2, wherein the ceramic material comprises a ceramic matrix and carbon and / or ceramic fibers incorporated in this ceramic matrix. 4. A gas injection system (1) for injecting gas into a regenerator of a fluid catalytic cracking unit, said system comprising at least one injection element (10, 10 ') according to one of the Claims 1 to 3 and the support (11, 11 '). Injection system (1) according to claim 4, wherein for at least one injection element (10; 10 '), the injection system comprises a fixing device (14; 14') of said injection element. injection 3024053 on the support (11; 11 '), said fixing device being able to absorb a difference in expansion between the support material and the ceramic material of said injection element. 5 6. Injection system (1) according to claim 5, wherein for at least one injection element (10; 10 '), the fixing device comprises at least one plating element (14; 14') capable of exerting a force on this injection element to press this injection element against the support (11; 11 '). 10 Injection system (1) according to claim 6, wherein the plating element comprises a tab (14; 14 ') welded at one end to the support (11; 11') and the other end (21; ) is able to exert an elastic bearing force on the injection element (10; 10 ') 15 when said injection element is installed on the support. 8. Injection system (1) according to one of claims 4 to 7, wherein the carrier comprises a perforated tray (11; 11 ') arranged to cover the entirety of a section of an enclosure (101) regenerator (100) to support the fluidized catalyst bed (102). 9. A method of manufacturing a gas injection element (10) for a regenerator of a fluid catalytic cracking unit, so that this element defines a passage (12) for the gas, intended to unblock. a part to a cavity, and secondly to a fluidized bed, the method being characterized in that the injection element is made of ceramic material. 10. The manufacturing method according to claim 9, comprising a step of sintering SiC silicon carbide particles.